How to deal with the excessive water content of the recovered solvent? Direct answer: Where does the water come from first-the intake water, the mixing of the condensation link, and the breathing condensation of the storage tank are the three main sources, and the treatment path is different for different sources; the treatment method is selected according to the mutual solubility of the solvent and water, and the layered system can be solved by static sedimentation plus water discharge, while the non-layered system should go azeotropic distillation or adsorption dehydration. Prevention is cheaper than treatment: control the humidity of the intake air, timely discharge of liquid in the separation section, and good breathing management in the storage tank. Excessive water content rarely occurs. In this paper, the selection of dehydration methods and preventive configuration are clarified for the reference of quality and operation and maintenance personnel.
The investigation of water exceeding the standard starts from the source: water is taken in the air, the material itself contains water or water vapor is brought in from the process, which will condense out together during condensation; Condensation is mixed, the discharge of liquid in the separation section of the device is not timely, and the water phase and solvent are mixed and carried out. The temperature difference between day and night causes the water vapor in the tank to condense and drip on the top of the tank, increasing water content for a long time. The disposal actions of the three sources are different. Mixed treatment is equal to white dry-check the source while measuring the moisture content of the batch, blocking the source is better than repeated dehydration. There is another advantage to finding out the source: knowing which way the water comes in, the transformation investment can be concentrated in one place, rather than sprinkling pepper on the whole process.
The layered system is easy to handle: the solvent and water are not miscible, and the water can be cut in the separation section after standing and settling, and the automatic water cutter can save labor. The non-layered system needs to move the process: a solvent that forms an azeotrope with water, and the water is taken out and separated by azeotropic distillation; Deep removal of trace water uses adsorption dehydration, and molecular sieve or desiccant is regenerated periodically. For systems that are sensitive to water and have high quality requirements, pervaporation membrane is also a mature option, and the energy consumption is lower than that of distillation route. The cost of wrong selection of the method is that the energy consumption is doubled and it is not clean. Before selection, make clear the compatibility relationship between solvent and water, or do a small test to verify it.
There are three prevention and configuration pipes: on the air inlet side, gas-liquid separation is carried out before entering the device in the process link with high moisture, and water vapor is not allowed to condense together with solvent gas; On the separation side, the drain port of the condensation separation section is kept unobstructed, the upper and lower limits are set, and the condensate is cut off in time to prevent the two-phase mixing time from being too long. On the storage side, add nitrogen seal or dry respirator to the solvent recovery tank. The three gates are fully equipped, the water content is stable at a low level for a long time, and the burden on the dehydration device is also small. Most of the preventive configuration is a long-term benefit of one investment, spread the account to three years, than repeated dehydration, repeated rework of the processing costs are much lower.
| Method | applicable system | Features |
|---|---|---|
| Static water cutting | immiscible layered system | Low cost to manage |
| azeotropic distillation | azeotropic system | High energy consumption and reliable effect |
| Adsorption dehydration | deep removal of trace water | Desiccant to be regenerated |
| pervaporation membrane | High quality requirement system | Low energy consumption, high investment |
| Intake gas-liquid separation | Wet working condition | Small preventive investment |
| nitrogen-sealed dry respiration | Storage link | condensation-breaking pathway |
The caliber of the reuse process shall prevail: the sensitivity of different processes to moisture varies greatly, and the downstream allowable value is the upper limit.
The water phase usually contains a small amount of solvent and impurities, which are disposed of according to the requirements of wastewater management, and the secondary recovery of solvent in the water phase is conditional. Direct discharge has both environmental protection risks and loss of solvent, thus losing both ends of the account.
Yes. Water vapor is more likely to condense out at low temperature, and condensation on the top of the tank and liquid accumulation at the low point of the pipeline are aggravated. A special inspection of drainage and sealing before winter can push down more than half of the seasonal excess.
This article by LuoyangWohong PetrochemicalEquipment Co., Ltd. arranges that the company provides design, manufacturing and operation and maintenance services for condensation recovery, membrane separation recovery and complete solvent recovery devices for chemical and pharmaceutical enterprises. If you need process evaluation or scheme configuration, please contact and exchange.
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